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US Muon Accelerator Program Report

Revised Completion Plan for the Muon Ionization Cooling

Experiment (MICE) at Rutherford Appleton Laboratory

Submitted to the US Department of Energy by the US Muon Accelerator Program in response to the DOE program review on August 12–14, 2014

Report Date: September 15, 20141. IntroductionThis report has been generated in response to the Technical and Management Review of the US Muon Accelerator Program conducted by the US Department of Energy Office of High Energy Physics on August 12–14, 2014. As stated in the review charge, the review was carried out…

in response to the US Particle Physics Project Prioritization Panel (P5) Report1 which recommended to:

Reassess the Muon Accelerator Program (MAP). Incorporate into the GARD programthe MAP activities that are of general importance to accelerator R&D, and consult withinternational partners on the early termination of MICE.

In particular, the panel recommends to "realign activities in accelerator R&D with the P5 strategic plan. Redirect muon collider R&D and consult with international partners on the earlytermination of the MICE muon cooling R&D facility."

A key outcome of the review was the action item:

Present to DOE a detailed plan for Step 3π/2 by 15 September 2014.

This report describes that plan, which aims for the completion of MAP-supported participation in the Muon Ionization Cooling Experiment (MICE) with a demonstration of the full cooling process, including RF re-acceleration, on the 2017 timescale. It also targets a ramp-down of the other elements of the MAP research effort over roughly the next year with the goal of providing a suitable transition period for our early career researchers. We believe this plan will result in a successful demonstration of the muon ionization cooling process while fitting within the constraints specified by the US DOE.

1 “Building for Discovery: Strategic Plan for U.S. Particle Physics in the Global Context”, http://science.energy.gov/~/media/hep/hepap/pdf/May%202014/FINAL_P5_Report_053014.pdf

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http://science.energy.gov/~/media/hep/hepap/pdf/May%202014/FINAL_P5_Report_053014.pdf


2. OverviewThe Muon Ionization Cooling Experiment proposal2 defined a staged deployment of the ionization cooling channel elements to support an experimental program in 6 steps (see Figure 1) at the Rutherford Appleton Laboratory (RAL). The optics were based on the 201 MHz RF SFOFO cooling channel that was developed as part of the US Feasibility Study II3. Table 1 summarizes the key top-level experimental deliverables that would be provided by each step.

Due to challenges with the construction schedule, primarily associated with fabrication of the superconducting magnets, the collaboration opted for a streamlined experimental plan. As of the November 2013 MICE Project Board Review and the February 2014 DOE review of MAP, that plan envisioned Step I (already complete), Step IV operations during the 2015–16 timeframe, and Step VI operations starting sometime in 2019. In April 2014, revised budget guidance from the DOE Office of High Energy Physics forced reconsideration of this plan and the MICE Project Board endorsed development of a revised plan that could conclude at Step V, to save both money and time, while preserving the critical demonstration of the full ionization cooling process including RF re-acceleration. In May 2014, the P5 recommendation to negotiate a rapid conclusion of the MICE experiment appeared and the August DOE review was convened to evaluate whether a 3-year plan could accommodate Step IV and/or Step V.

Figure 1: The six experimental steps as envisioned in the MICE proposal. Step I has been completed and due to the fabrication schedule of the magnets, Steps II and III have been skipped with Step IV to begin

2 “An International Muon Ionization Cooling Experiment (MICE),” Proposal to Rutherford Appleton Laboratory, http://mice.iit.edu/micenotes/public/pdf/MICE0021/MICE0021.pdf3 “Feasibility Study-II of a Muon-Based Neutrino Source,” S. Ozaki, R. Palmer, M. Zisman, and J. Gallardo, eds., BNL-52623, June 2001, http://www.cap.bnl.gov/mumu/studyii/FS2-report.html

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http://www.cap.bnl.gov/mumu/studyii/FS2-report.html

http://mice.iit.edu/micenotes/public/pdf/MICE0021/MICE0021.pdf


commissioning early in calendar 2015. The originally envisioned Step V would provide a demonstration of emittance cooling with RF re-acceleration while Step VI would provide a full cell of the cooling channel envisioned for the neutrino factory design of the US Feasibility Study II.

Table 1: Key experimental deliverables of the 6 steps originally envisioned for the MICE Experiment.

Deliverable Step I Step II

Step III

Step IV

Step V

Step VI

Characterization of TOF and PID systems and muon beam Characterization of Spectrometer Solenoid and Tracker Performance

Measurement of Material Properties that Determine Ionization Cooling Efficacy: Energy Loss and Multiple Scattering

Demonstration of Emittance Cooling with RF Re-acceleration

Characterization of SFOFO Cooling Channel Optics (based on Study II) with canonical momentum control and full optics flexibility

The MAP position on the MICE experiment is that a demonstration of the full ionization cooling process (i.e., emittance cooling combined with RF re-acceleration) must be completed for MICE to be concluded successfully. In Table 1, this corresponds to completion of Step V. However, the members of the August 2014 review committee indicated extreme skepticism that declining US support would allow this to be achieved with Step V given both the budget profile being proposed by DOE (which would severely restrict US experimental support) and the 3-year timeframe prescribed (which would likely result in very limited US laboratory support to be available for Step V operations). Finally, the committee expressed concerns that the remaining R&D risks associated with the RF–Coupling Coil (RFCC) module could be adequately managed within the 3-year timeframe. With these concerns, the MICE team at the review carried out a preliminary assessment of whether a demonstration of emittance cooling with RF re-acceleration could be provided with components already largely in hand and within the 3-year timeframe specified by the US DOE. The resulting concept has been (temporarily) labeled MICE Step 3π/2. Over the course of the last month, this concept has been evaluated in greater detail as described below.

The MICE Step 3/2 plan aims to utilize the complement of magnets presently available for the experiment, consisting of two spectrometer solenoids delivered by the US team and two focus coils provided by the UK team, as well as the hardware for 2 RF cavities on the beam line which is already largely in hand. This eliminates the US risks associated with assembly of the RFCC module and the UK effort required to modify the MICE Hall at RAL to accommodate the RFCC and the required magnetic shielding which would surround it in the Step V configuration. Figure 2 shows the generalized layout that has been pursued in order to evaluate the relevant beam line optics. It should be noted that this generalized configuration actually has closer resemblance to the optics of “modern” neutrino factory cooling channel designs being considered by the IDS-NF study4 as well as by the Muon Accelerator Staging Study (MASS) within MAP. The revised configuration will require an alternative design for a Partial Return Yoke (PRY) for the beam line to be developed – a relatively straightforward engineering exercise which is significantly less expensive than that of the Step V configuration. Furthermore, additional absorbers may need to be procured in order to successfully execute the plan. The additional absorbers offer negligible project risk and budget impact.

4 IDS-NF “Interim Design Report,” http://arxiv.org/abs/1112.2853

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http://arxiv.org/abs/1112.2853


Figure 2: A generalized layout of the proposed cooling channel showing the position of the coils in each of the spectrometer solenoid and focus coil magnets. The three gaps shown provide space to match the lattice parameters for the cooling demonstration and for inclusion of the necessary RF and absorber elements.

The following sections describe the optics and project impacts of executing this step as the conclusion of the MICE demonstration. Our evaluation indicates that a successful demonstration of the ionization cooling process can be achieved with this configuration within the timeframe mandated by the DOE budget profile for concluding the MAP effort.

3. MICE Optics SummaryIn order to reduce the R&D risks associated with completion of MICE, the MICE optics team has focused on Step 3π/2 options that make use of existing designs and hardware. The upshot is that such options indeed exist and are suitable for the key MICE deliverable: the demonstration of muon ionization cooling with RF re-acceleration.

3.1 Optics in the MICE Channel With and Without the RFCC ModuleIn the original design of Step V (shown schematically in Figure 3), an RFCC module containing four RF cavities is placed between two Absorber–Focus Coil (AFC) modules each housing absorbers made of either liquid hydrogen (LH2) or lithium hydride (LiH). The cavities are surrounded by the CC magnet, which immerses them in a multi-tesla magnetic field.

Figure 3: The conceptual layout of MICE at Step V, including upstream and downstream Spectrometer Solenoids (coils indicated in red), two AFCs (green) housing absorbers, and central RFCC with four RF cavities surrounded by the CC magnet (orange).

The CC magnet allows the transverse betatron function in the solenoidal channel to be matched between two waists with small beta function (42 cm in the baseline Step V case) located within the absorbers inside the upstream and downstream AFC modules, while simultaneously limiting the maximum value of beta inside the cavities to the acceptable limits set by the cavity aperture. This effectively means that there is a maximum of the beta function near the center of the CC magnet, as indicated in Figure 4.

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If the CC magnet is not present, it is no longer possible to have a maximum of the beta function between the two AFC modules. This also means that, assuming the symmetry of the beta function in the MICE channel, the maximum beta is now located at the AFC coils. Efficient ionization cooling requires that the beta function be as small as possible at the absorber positions, therefore the absorbers are no longer ideally positioned within the AFC module and should be placed at other locations with sufficiently small beta values.

As the starting point for developing suitable lattice solutions for Step 3/2, a geometry has been considered consisting of two Spectrometer Solenoids at the upstream and downstream ends of the MICE Channel and two AFC magnets in between with three additional drift regions as shown in Figure 5. Absorbers and RF cavities could be placed in these drift regions. Two lattice solutions have been identified, which will allow MICE Step 3/2 to successfully accomplish the proof-of-principle demonstration of ionization cooling with RF re-acceleration. These solutions are briefly discussed in the following sections.

Figure 4: The optics in the MICE Step V Channel.

Figure 5: The preliminary geometry illustrating the focusing system of the potential Step 3π/2 consisting of SSs and AFCs, with dashed rounded rectangles indicating the available space for absorbers and RF cavities.

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3.2 Reference lattice for Step 3/2The reference lattice solution for Step 3/2 is realized by centering the main absorber in the drift space between the two AFC magnets, where a low-beta region naturally arises, and placing single RF cavity modules in the drift regions between the AFCs and the SSs. The distance between the AFCs was set so as to accommodate the LH2 absorber. It should be noted that two additional short absorbers may be necessary in order to shield the two Trackers from dark current induced radiation. These absorbers would ideally be made of LiH, however plastic can also be considered. The layout of the reference lattice is shown in Figure 6.

Figure 6: The layout of the reference lattice design for Step 3π/2.

The optics in the reference lattice solution allow matching of the beta function to relatively low values in the main absorber (42 cm at 140 MeV/c, 55 cm at 200 MeV/c, and 70 cm at 240 MeV/c) while maintaining large acceptance through the channel. At present the most thoroughly investigated AFC magnetic field polarity configuration is “+,–,–,+” (i.e., the solenoidal magnetic field is oriented along the beam axis in the outer two AFC coils and opposite the beam axis in the inner two coils), which allows smaller values of the beta function (both at the absorber and at the AFC) than the “+,+,–,–” case. The beta functions for different momentum and polarity settings are shown in Figure 7 and the corresponding magnetic fields in Figure 8.

The reference lattice requires one main absorber, and two single cavity modules, of which a prototype is already in operation at the Fermilab MTA. The reference lattice has sufficient flexibility in the choice of optical settings to allow a successful demonstration of ionization cooling. Detailed tracking studies have been started, with promising results. One study was performed using the MICE-standard code MAUS (MICE Analysis User Software). It performs stepwise tracking through the non-linear magnetic field of the magnets and EM fields of the RF cavities, including such details of the lattice geometry as aperture limitations and effect of materials (absorbers, Tracker planes, and RF and safety windows), using realistic models of the relevant physics processes (energy loss, straggling and multiple scattering). The evolution of muon energy as the beam traverses the MICE Step 3/2, channel based on the reference lattice, is shown in Figure 9. The two accelerating cavities, operating with gradients of 10.3 MV/m (in order to allow for tuning head room and RF losses in the distribution system), partially restore the energy lost in the main LiH absorber. These effects can be clearly seen in Figure 9 together with the small effects due to additional materials in the beam path. The evolution of transverse emittance shown in Figure 10 indicates a clearly measurable emittance reduction. The amount of cooling is marginally increased by adding absorbers outboard of the RF cavities. These absorbers will also shield the tracker detectors against dark current induced radiation. This study was performed using the reference lattice with “+,–,–,+” polarity using an asymmetric matching to take into account the asymmetric energy profile (shown in Figure 9), with beam momentum of 200 MeV/c and input normalized 4D emittance of 6 mm·rad. Other beam configurations are also being studied with encouraging results.

A second tracking study of the reference lattice was performed utilizing ICOOL and G4beamline. ICOOL was used to generate the input particle distributions, and G4beamline for the actual tracking. Stochastic effects such as multiple scattering and energy straggling were taken into account. The aperture limitation was set to a radius of 20 cm everywhere in the channel. In contrast to the MAUS study, no other materials besides the central LiH absorber (65 mm) were included. The missing materials would

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include, in particular, the scintillating fiber tracker planes in the spectrometer solenoids as well as RF and absorber windows.

The other key parameters of the distribution and lattice are as follows:

transverse beam spread: σx = σy = 32.34 mm, σPx = σPy = 19.6 MeV/c; longitudinal beam spread: σPz = 2 MeV/c, σt = 0.15 ns; longitudinal momentum: Pz = 200 MeV/c; initial normalized 4D emittance: 6π mm·rad; 10,000 particles simulated; LiH absorber density is 0.693 g/cm3 (different from MAUS or G4beamline defaults; based on the

actual measured density of the absorber as fabricated); RF gradient = 10.3 MV/m, on-crest acceleration.

The beam starts at the center of the upstream spectrometer solenoid central coil, and the distribution is produced assuming a 4 T field where particles are generated.

Figure 11 shows the magnetic field on axis and resulting beta values. As in the MAUS study, the ICOOL/G4beamline study (carried out by members of the US MAP cooling group) shows good cooling performance, which, as seen in Figure 12, is measurable in MICE with high significance. The study also indicates good beam transmission (Figure 13) for the MICE-nominal 6π mm·rad input emittance. Minor discrepancies between the results of the two studies will be carefully studied over the coming weeks; some of these may be attributable to slight differences in LiH composition used in the two simulations, the slightly different beta profile vs. z obtained with G4beamline, and the inclusion of windows and Tracker planes in the MAUS simulation. However, even at this early stage of analysis, the results from these two independent simulations support the conclusion that MICE Step 3π/2 will achieve its goals.

An alternate lattice configuration has also been studied but appears to have less flexibility than the reference lattice. It assumes a two-RF-cavity module with space for an absorber between the cavities located at the center of the channel. Final optics specifications will be made on the basis of further assessment of the performance and engineering constraints.

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Figure 7: Betatron functions in the MAUS simulation of the reference lattice for “+,–,–,+” polarity for 140, 200 and 240 MeV/c settings (shown in black) and for “+,+,–,–” polarity for 200 MeV/c (red dashed curve).

Figure 8: Magnetic field on axis in the MAUS simulation of the reference lattice for “+,–,–,+” polarity and settings for 140, 200 and 240 MeV/c (shown in black) and for “+,+,–,–” polarity for 200 MeV/c (red dashed curve).

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z [m]

Figure 9: The evolution of mean total energy (in MeV) in the MAUS simulation along the length (in m) of the MICE Step 3/2 channel using the reference lattice configuration.

z [m]

Figure 10: The evolution of 4D normalized RMS emittance (in mm·rad) in the MAUS simulation along the length (in m) of the MICE Step 3/2 channel in the reference lattice configuration, with “before” and “after” error bars indicated in dark blue (at the “Tracker Reference Plane” locations, z = ±3.4 m). The measurable emittance reduction is clearly visible.

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Figure 11: (left) longitudinal magnetic field on-axis and (right) transverse betatron function vs. z in ICOOL/G4beamline tracking study of reference lattice with beam parameters as given in text.

Figure 12: (left) average momentum and (right) normalized transverse emittance vs. z in ICOOL/G4beamline tracking study of reference lattice with beam parameters as given in text.

Figure 13: Muon transmission efficiency vs. z in ICOOL/G4beamline tracking study of reference lattice with beam parameters as given in text.

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3.3 ConclusionsTwo candidate lattices for Step 3/2 have been studied in some detail. The reference solution offers greater flexibility in beta function choice at the absorber position, and potentially offers engineering simplifications as well (it uses only the already-designed single RF cavity modules, of which one has already been built). However, both solutions are in principle suitable for use at Step 3/2 for the first demonstration of sustainable ionization cooling of muon beams. Optics studies will continue, with final specifications to be reported at the next (25/26 November 2014) MICE Project Board review.

4. The Revised MICE Project PlanThe changes from the Step V arrangement of the MICE experiment to the proposed Step 3π/2 are significant. Major changes in the hardware required have reduced the timescale for deploying the final MICE configuration and have greatly reduced the costs and risks for both the US and UK programs.

4.1 Summary of Modifications to UK Project PlanThe following sections identify the main activities that have been reduced or removed from the project’s scope with a short description of the resulting changes in effort and timescale. The primary UK schedule drivers that remain are also identified.

4.1.1 Installation of the RFCC In the Step 3/2 configuration, the US-supplied RFCC module is eliminated. The assembly of the RFCC represented a very large and complex activity. Experience gained from the assembly of the Single Cavity Test System, at the Fermi National Accelerator Laboratory, gave an insight into the amount of work required to assemble the full RFCC system at RAL. Major required activities would have included:

Changes to the roadway outside the experimental hall at RAL as well as substantial modifications to the hall itself;

Installation of extensive support services for the RFCC in the experimental hall.Thus the elimination of the RFCC as part of the MICE optics dramatically reduces the budget, timescale and risk required for implementing the final MICE configuration.

4.1.2 Installation of the Second Liquid Hydrogen SystemThe proposed Step 3π/2 arrangement of the MICE cooling channel utilizes lithium hydride (LiH) as the main absorber material in place of the originally scoped liquid hydrogen (LH2) absorber system. With this change in absorber medium the second LH2 system will no longer be required. The timescale and cost savings are not just in the hardware and effort associated with the construction of the hydrogen panel, control systems and contained exhaust system, but also in the extensive safety requirements in the design, construction and operation of the hydrogen system.

4.1.3 Schedule DriversThe analysis of the proposed schedule to deploy Step 3π/2 shows that the main driver for the project’s critical path is now the installation and commissioning of the two RF systems required to drive the two RF cavities in the new layout. The work in advance of the installation is being carried out at the Daresbury Laboratory (DL), Warrington, where the buildup and initial testing to 2 MW, into a dummy load, will be completed. The first of the amplifier systems was successfully tested at DL to 2 MW and in the MICE Hall at RAL to a power of 500 kW into dummy loads. Following the power tests, the control racks and the model 4616 amplifier were removed and transferred back to DL for testing with the second TH116 amplifier.

During the lead-up to completion of the construction of the Step IV arrangement of the experiment, the DL effort (from the Electrical Engineering department) was to concentrate on the current step. With the schedule as it was for the preparation and installation of Step V, work could be carried out sequentially: Step IV installation and then RF preparations and operations, followed by Step V preparation. With the

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expeditious nature of the schedule to complete the MICE project that is now proposed this is no longer the case and significant pressure is bearing on the electrical group to work both on the electrical installation work at RAL and electrical preparation work for the RF systems at Daresbury.

4.1.4 Schedule AssumptionsThe critical path (see Table 3 and Figure 14) has been constructed by changing the amount of data taking in the Step IV arrangement to utilize all slack up to the completion of the Step 3π/2 arrangement. The slack is created due to the delivery and subsequent installation of the RF systems, RF system 2 being the last part delivered and installed on-site at RAL. Following the RF system installation the low and high power testing can commence and the commissioning of the whole channel can follow.

In this analysis, the absolute latest date for delivery of the RF cavities and associated chambers can be found. The same is true for the PRY South and North frames and plates.

From the schedule analysis the following dates have been found:

Construction and Commissioning (taking ALL slack in the schedule)

Step IV Construction complete – 25th May 2015 Step IV Commissioning complete – 3rd August 2015 Step IV De-commissioning start – 2nd June 2016 Step 3π/2 Construction complete – 27th March 2017 Step 3π/2 Commissioning complete – 3rd May 2017

Data-taking periods (taking ALL slack in the schedule)

Step IV data taking – 3rd August 2015 to 2nd June 2016 Step 3π/2 data-taking period – 3rd May 2017 to 31st March 2018 (end of the UK financial year)

Latest date for Step 3π/2 equipment delivery to RAL (taking ALL slack in the schedule)

RF Cavities and associated chambers – 1st November 2016 South PRY Frame – 15th October 2016 South PRY Plates – 26th October 2016 North PRY Frame – 1st January 2017 North PRY Plates – 10th January 2017

All tasks in the schedule have 35% time contingency added.

Interface dates defined for the planned delivery of the Step 3π/2 equipment – Arrival at RAL

RF Cavities and associated chambers – 26th April 2016 South PRY Frame – 29th March 2016 South PRY Plates – 29th March 2016 North PRY Frame – 29th March 2016 North PRY Plates – 29th March 2016

Thus all US deliverables should arrive with at least 6 months of slack before their scheduled installation dates at RAL.

As already stated the schedule has removed all slack to define the latest dates for delivery of the RF cavities and chambers and the Partial Return Yoke. The period for data taking needs to be discussed by

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the collaboration to ascertain the correct and required length of data taking. Even with a shortened data-taking period there will still be a substantial period of data taking available.

The data-taking period for the Step 3π/2 arrangement will terminate at the end of the UK 17/18 (March 18) financial year.

4.1.5 Possible expeditersThe RF-system installation is found to be the main driver of the critical path. The initial buildup and test of the second amplifier system at the Daresbury Laboratory must be carried out before delivery to RAL. It is at this stage that resource limitations impact the schedule. During this period additional staff applied to the tasks would shorten the duration of each activity. Any technical expertise that could be brought to bear from collaborating institutes in the Electrical and RF disciplines would expedite the schedule. It has been estimated that two electrical technicians and two RF experts would be required to expedite the schedule and bring forward the completion date. Additional analysis of the RF-work-package resource-loaded schedule and discussions with senior management at the Daresbury Laboratory must take place to fully validate these estimates.

4.1.6 RisksAs noted previously, the elimination of the RFCC module along with the second liquid hydrogen system significantly reduces the risks associated with the UK effort. Table 4 shows the UK project risk assessment before and after implementation of the Step 3π/2 plan. A dramatic reduction in the major UK risks is clearly shown.

4.1.7 ConclusionThe project plan proposed here has many cost-and-schedule advantages and also offers some advantages for the experimental effort. The plan as proposed shows the very latest dates for the completion of the sub-projects. It can be seen that a data-taking period of 10 months in the Step IV arrangement is possible. This run will allow significant knowledge of the operation of the magnets in a lattice to be gained and will provide data with liquid-hydrogen and lithium-hydride absorbers. The experience of operating the lattice can be applied directly to Step 3π/2 and will therefore reduce risks associated with commissioning and operating Step 3π/2. The operational period shown for Step 3π/2 will terminate at the end of UK financial year 2017/18.

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Table 2: UK budget summary

Table 3: Critical path

Figure 14: Critical path chart

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Table 4: UK Risk Register. Risk scores on the left correspond to the Step V configuration, while the scores on the right show the reduction in risk associated with the Step 3π/2 implementation.

4.2 US Construction Project ModificationsModifications in the US plan include major changes to the originally planned magnet, partial return yoke (PRY) and RF systems.

4.2.1 MagnetsWith the adoption of the new Step 3π/2 configuration, the US construction project has dropped the Coupling Coil (as well as the RFCC module of which it was a part). Thus all MICE magnets for which the US is responsible have been delivered to Rutherford Appleton Laboratory, having passed all acceptance criteria at the vendor prior to shipment. The only remaining US construction project magnet task is commissioning of the two Spectrometer Solenoids in the MICE hall.

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4.2.2 Magnetic Mitigation - Partial Return Yoke (PRY)The orders for the steel and the component fabrication for the Step IV PRY configuration are in the hands of the vendors. Fabrication of the framework parts is proceeding on schedule at Keller Technology with the south side framework already completed. The 50 mm thick steel plates from JFE Steel Corporation in Japan are complete. The heat treatment for the 100 mm plates has started and they are expected to be complete by the end of September 2014. Design work on the PRY extension for Step 3π/2 will begin as soon as the lattice layout is complete. We plan to utilize the same vendors (for steel and fabrication) for the Step 3π/2 PRY extension.

4.2.3 RFAs shown in the Step 3π/2 lattice configuration (see Figure 6), the RF part of the RFCC module is being replaced by two single cavity 201 MHz RF modules. Each module will contain one cavity and one absorber disk (LiH or plastic). The single cavity test system (SCTS) currently operating in the MuCool Test Area (MTA) at Fermilab (see Figure 15) is a very close approximation to what will be needed for MICE Step 3π/2.

Figure 15: SCTS in the MTA

The production prototype cavity has already reached 8 MV/m (the original MICE specification) in the absence of an external magnetic field. Once the Step 3π/2 lattice configuration has been finalized, design modification of the existing SCTS vacuum vessel will begin. The cavity bodies, tuners, windows and RF power ceramic windows exist. Four new RF power couplers and 12 tuner actuators will have to be fabricated. We have production designs for the actuators and RF power couplers (for SCTS tests), but will wait for the results from the SCTS tests with B field before launching full production. Component fabrication can begin as soon as funds are available.

4.3 US Construction Budget OverviewIn response to the May 2014 P5 Report and the August 2014 DOE Review, the US MAP program received DOE budgetary guidance to expect $9M, $6M, and $3M in FY15, FY16, and FY17, respectively. US MAP has been redefined to conclude the design and simulation efforts, now called Advanced Muon and Neutrino Sources, at the end of FY15 and to conclude the studies of the operation of Vacuum and High Pressure RF Cavities by the middle of FY16. These ramp-down timescales were

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chosen to allow the early career researchers to complete the studies started in prior years. This new budgetary guidance maintains the operations of the MuCool Test Area (MTA) through the middle of FY16 to ensure its availability for the testing and characterization of the MICE RF components. In addition, these funds include support for US MICE Experimental Support through the end of FY17. US MICE Construction will continue through FY17 for installation and commissioning after delivery of the remaining major US supplied systems:

Step IV Partial Return Yoke (PRY) Magnetic Shielding – March 2015 Step 3π/2 PRY – March 2016 RF Modules #1 and #2 – April 2016.

An R&D Risk of $537K (Risk Estimate × Probability of occurrence) is included in FY16. The total US MAP Budget for FY15 + FY16 + FY17 is under the three-year DOE guidance of $18M, but is ~2% above the FY15 guidance of $9M. A summary of the proposed US MAP Budget for FY15–17 is shown in Table 5.

Table 5: US MAP Budget Summary for US FY15–17

4.4 Key Project Evaluation CriteriaWe distinguish R&D Risk from Contingency. Contingency is the typical project construction contingency based on incomplete specifications or design, and uncertainty in the cost estimate or in the time that will be required to perform a given task. Typically, this US MICE estimate includes a 30% contingency in the cost estimate and 40% contingency in US$ for labor. There is also an overall time contingency added to the time required to do a related series of tasks. This appears in the US MICE

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Project Plan as the difference between the “Required” (with time contingency) and the “Ready” (without time contingency) dates.

R&D Risks are different in nature. They are cost and time estimates of what might be needed to mitigate the unknown problems that might be encountered in performing a new type of task for the first time. While the contingency is included in the baseline MICE Project Plan cost estimate and schedule, the R&D Risk is not. It is tabulated and added separately. As the MICE construction project has progressed and the definition of the MICE program has matured, many of the original R&D Risks considered through MICE Step VI have either been faced and overcome or “retired,” sometimes accruing part of the Risk estimated cost, or have been removed as the MICE program has changed from Step VI to Step V to Step 3π/2. In November 2013, the initial Risk Register consisted of 21 identified R&D Risks, with an estimate of $10.4M to mitigate or respond to a realized Risk. As a first order estimate, we assumed that only ½ of these Risks would be realized, so provided a Risk allowance of 50%*$10.4M = $5.2M. Since then, we added another Risk, and retired 10 of the Risks at an accrued cost of $973K compared to a Risk estimate of $3.1M, or a ratio of accrued to estimate of 31% (compared to our 50% assumption).

The decision to limit MICE to Step 3π/2, using only two single RF cavity modules, has greatly reduced the US MICE cost, complexity, and R&D Risks. Thus we have re-evaluated the Risk Register for Step 3π/2 obtaining 9 identified risks with a total cost estimate of just over $1.6M (with a probability weighted impact of $537K). It is important to note that the risk ranking of the identified risks are generally in the low to moderate range with no severe risks remaining. The removal of the Coupling Coil Magnet (CCM) has removed the risks of cryostating, testing, and integrating and commissioning the CCM, while also greatly reducing the scope and risk of the Partial Return Yoke (PRY) magnetic shielding from that of Step V. Now PRY Step 3π/2 is only a 40% linear extension of the PRY Step IV and the design and installation plans and experience of PRY IV are directly applicable to PRY 3π/2 with minimum risk. Moreover, the removal of the CCM means that the RF cavities will experience only the fields of the Absorber Focus Coil (AFC) magnets. The Single Cavity Test System (SCTS), using the prototype 201 MHz RF cavities, couplers, actuators, etc., is currently operating in the MuCool Test Area (MTA), and will operate using the MTA magnet, which was the prototype for the AFC. Therefore the systems test with magnetic field of the SCTS at MTA will test a close approximation of the components and configuration (except without the PRY magnetic shielding of the couplers) as for the MICE production system and its operational conditions. The only difference between the SCTS and the production MICE RF Modules is in the vacuum end windows.

The updated active Risk Register for Step IV and Step 3π/2 is shown in Table 6. In this plan, all of the US construction risks are now in the low to moderate risk range and no high-risk items remain. The identified R&D Risks are of three types: system integration, SCTS testing, and RF Module production and assembly. The SCTS has successfully operated up to 8 MV/m and 1 MW power. Step 3π/2 requires 12 MV/m. Although testing in the magnetic field has not been done yet, testing with a similar prior RF cavity in this magnetic field has indicated that no problems should be anticipated. The successful assembly and operation of the SCTS using prototype MICE RF Module components has already been demonstrated. The system integration Risks will only be faced when the components are delivered, installed, and commissioned at RAL. The questions here will be whether the pieces fit together properly and whether there are unforeseen interactions between the Spectrometer Solenoid, AFC, RF Modules, and PRY systems. These will have to be addressed by sending engineers to RAL to assess and possibly make local field modifications, so a relatively large $ Risk estimate is retained.

A waterfall Gantt Chart of key construction project deliverables is shown in Table 7. Key dates for delivering US hardware to RAL are:

March 2, 2015 – completion of partial deliveries of Partial Return Yoke (PRY) for Step IV March 29, 2016 – delivery of Partial Return Yoke (PRY) for Step 3π/2

April 26, 2016 – delivery of MICE RF Module #1 and Module #2

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Table 6: US MICE Active Risk Register (rotated for ease of viewing). The risk scores correspond to a new evaluation for Step 3π/2 for which no high-risk items appear. Furthermore, the proposed mitigations are expected to be effective as demonstrated by the low post-action risk scores.

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Table 7: US MAP Milestones (“Waterfall Plot”) (rotated for ease of viewing).

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5. ConclusionIn response to the recommendations and action item identified by the August 2014 DOE Review Committee, the Muon Accelerator Program (MAP), the MICE International Project Office (MIPO) and MICE Experimental Management Office (MEMO) have prepared a plan to complete the demonstration of the muon ionization cooling process, i.e., the demonstration of transverse emittance cooling along with RF re-acceleration of the muons, on the 2017 timescale. An alternative to the MICE Step V layout and optics configuration (the temporarily named Step 3/2 layout), which has acceptable performance to complete this demonstration, has been developed. The baseline schedule for the expedited plan envisions:

Assembly and commissioning of MICE Step IV through July 2015; MICE Step IV Running from August 2015 to June 2016; Assembly and commissioning of the MICE Cooling Demonstration (i.e., the so-called 3/2

configuration) through April 2017; Start of the Cooling Demonstration in May 2017.

The more rapid deployment of the experimental steps has been achieved by focusing on the innovative use of hardware that is in hand or which is ready for assembly, thus minimizing further component design and construction activities. Our conclusion is that this plan will achieve the necessary performance goals while fitting within both the time and budget constraints specified by DOE and the review committee for the successful conclusion of the MICE demonstration and the ramp-down of all MAP effort.

It should be noted that the above plan for the early conclusion of the MICE demonstration has been assembled quite rapidly – from April to August 2014, modifications were made to the MICE baseline plan to conclude the experiment with the Step V configuration in lieu of Step VI. The present exercise, which has spanned roughly one month, has led to further very substantial changes in both the construction and experimental plan. While we consider our conclusions about the acceptability of the plan to be strongly justified, further design optimization and a thorough review of the updated construction and experimental plans, including a detailed review of the proposed intermediate milestones required to evaluate progress, are required. Thus the MAP, MIPO and MEMO intend to solicit comment from the members of the MICE collaboration through the time of the next MICE collaboration meeting (MICE CM40, October 26–29, 2014) and to prepare a final version of the plan for review by the MICE Project Board and Resource-Loaded Schedule Review Committees at their next scheduled review (November 24–25, 2014 at RAL).

In light of the dramatic modifications embodied in this plan to successfully conclude the MICE ionization cooling demonstration, a recap that summarizes the major choices, trade-offs, and potential areas for further discussion is in order.

In particular, the plan aims for a demonstration that is “good enough” leading to a number of baseline choices intended to expedite and simplify the remaining construction effort:

Key choices for the US plan:o Eliminate the use of the RFCC module, thus eliminating the majority of the remaining

construction project risks for magnets;o Proceed with fabrication of two single-cavity RF modules (in lieu of a multi-cavity

module), which differ only marginally from the Single Cavity Test System (SCTS) currently operating in the MTA;

o Execute the next-generation PRY design (i.e., without the Coupling Coil magnet) utilizing key design elements of the Step IV PRY design which is presently in fabrication;

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o Prepare to run RF cavities in magnetic field at higher operating gradients for MICE (potentially as high as 16 MV/m). This requires an updated experimental plan for tests of the SCTS in the MTA, which, with contingency, should fit within an 18 month operating window for that facility.

Key choices for the UK plan:o Eliminate extensive MICE Hall infrastructure modifications required to accommodate the

RFCC module and associated Partial Return Yoke;o Eliminate integration activities required to accommodate the RFCC module;o Eliminate plans for fabricating and commissioning a second LH2 system.

Overall these modifications significantly reduce the both the cost and time required to achieve the cooling demonstration for both the US and UK efforts.

Risks associated with this plan have been dramatically reduced by eliminating the construction of any further novel hardware and adapting the cooling channel optics to utilize only components for which either prototypes and/or final production hardware already exist. In terms of the risks that remain, we note that the reference optics requires operation of the RF cavities at higher fields than planned for the MICE Step V configuration. However, the RF operating environment is reasonably approximated by the test configuration in the MTA and the higher gradients required are readily tested in the MTA. This results in a clear emphasis in the US plan to complete the MICE 201 MHz RF characterization in the MTA over the next approximately 12 months (18 months with contingency). Overall, the US effort now much more closely matches the configuration of a “typical” construction project in that the R&D risks are largely retired and the principal focus is on fabrication, assembly and delivery of well-understood components. Similarly, the focus of the UK effort shifts towards integration and exploitation of each of the key experimental configurations.

In conclusion, a plan has been prepared which we believe will result in a successful demonstration of the muon ionization cooling process, and which will support a productive ramp-down of the other elements of the MAP research effort, while fitting within the constraints specified by the US DOE. MAP efforts are now pivoting towards the execution of this plan.

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GLOSSARY#:4616: Tetrode vacuum tube used to drive the 2 MW TH116 in 201 MHz RF power

amplifier

C:Ckov: MICE aerogel-radiator threshold Cherenkov counter

D:Diffuser: Discs made of movable brass and tungsten “petals” that can be interposed into

the beam path in order to prepare beams with a range of input emittance.DL: Daresbury Laboratory, Warrington, UKDollar: U.S. currency denomination, approximately equivalent to 0.6 British Pounds.

E:Emittance: Generalized beam size in 6-dimensional phase-space, or a sub-space thereof.

F:FC: Focus Coil, magnet of the AFC module

G:G4beamline: Particle-tracking simulation code based on Geant 4 developed and maintained by

Muons, Inc.

I:ICOOL: Particle-tracking simulation code developed and maintained by BNL muon

cooling groupIonization cooling: Process of reducing beam emittance via ionization energy loss in low-Z absorbers

intermingled with RF re-acceleration.

L:LH2: liquid hydrogenLiH: lithium hydrideLLRF: low-level RF

M:MASS: Muon Accelerator Staging StudyMAUS: MICE Analysis User SoftwareMICE: Muon Ionization Cooling Experiment.MICE Steps: Partial implementations of MICE on the way to the planned, full implementation.MIPO: MICE International Project OfficeMEMO: MICE Experimental Management OfficeMTA: MuCool Test Area (at Fermilab)Muon: Elementary lepton, “2nd-generation electron.”

N:Normalized emittance: Geometrical emittance scaled by relativistic factor in order to compensate for

apparent increase or decrease of beam size in a focusing channel when energy is decreased or increased.

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P:PRY: Partial Return Yoke, used to suppress fringe fields from the MICE magnetic

channel that might otherwise affect the performance of electrical and electronic equipment in the MICE Hall.

R:RAL: Rutherford Appleton Laboratory, Oxfordshire, UKRF: radio frequencyRFCC: RF–Coupling Coil module

S:SFOFO: “Super-FOFO” cooling-channel lattice employing a double-resonance scheme in

order to reduce the betatron function value at the absorber locations.SS: Spectrometer SolenoidSCTS: Single-Cavity Test System

T:TH116: Thomson power triode providing 2 MW output power in 201 MHz RF power

amplifierTOF: Time-of-Flight scintillation-counter hodoscopeTracker: MICE 5-station scintillating-fiber track measurement system

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us - fermilab · web viewthe three gaps shown provide space to match the lattice parameters for the...

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